ko đăng linh tinh

ko đăng linh tinh 

Có (x + 15) ⋮ (x - 1)

<=> x - 1 + 16 ⋮ x - 1

<=> 16 ⋮ x - 1 (Vì x - 1 ⋮ x - 1)

<=> x - 1 ∈ Ư(16)

<=> x - 1 ∈ {1; 2; 4; 8; 16; -1; -2; -4; -8; -16}

<=> x ∈ {2; 3; 5; 9; 17; 0; -1; -3; -7; -15}

Mà x ∈ N => x ∈ {2;3;5;9;17;0}

\(A=\frac{1}{3}-\frac{1}{3^2}+\frac{1}{3^3}-\frac{1}{3^4}+...+\frac{1}{3^{99}}-\)\(\frac{1}{3^{100}}\)

=> \(\frac{1}{3}A=\frac{1}{3^2}-\frac{1}{3^3}+\frac{1}{3^4}-\frac{1}{3^5}+...+\frac{1}{3^{100}}-\frac{1}{3^{101}}\)

=> \(A+\frac{1}{3}A=\frac{1}{3}-\frac{1}{3^2}+...+\frac{1}{3^{99}}-\frac{1}{3^{100}}\)\(+\frac{1}{3^2}-\frac{1}{3^3}+...+\frac{1}{3^{100}}-\frac{1}{3^{101}}\)

=>\(\frac{4}{3}A=\frac{1}{3}-\frac{1}{3^{101}}\)

=>\(A=\frac{1}{4}-\frac{1}{3^{100}.4}\)

TL : 

=  -1 - 1/6

=   -7/6

HOK TỐT NHÉ^^^^^^^

=4,965186594.\(10^{-7}\)

Ta có:

A=/-x/ + 2x +5 = x +2x +5=3x +5

B= 4x -/x/+ 5=4x -x +5 = 3x +5

\(\Rightarrow\)A=B

Bài làm

Ta có: P = x³ + x²y - 2x² - xy - y² + 3y + x + 2017

          P = x³ + x²y - 2x² - xy - y² + 2y + y + x + 2017

          P = ( x³ + x²y − 2x² ) − ( xy + y² − 2y ) + ( x + y − 2 ) + 2019

          P = x²( x + y − 2 ) − y( x + y − 2 ) + ( x + y − 2 ) + 2019

Mà x + y = 2 => x + y - 2 = 0

Thay x + y - 2 = 0 và đa thức P, ta được:

P = x² . 0 - y . 0 + 0 + 2019

P = 0 - 0 + 0 + 2019

P = 2019

Vậy P = 2019 tại x + y = 2

# Học tốt #

\(P=x^3+x^2y-2x^2-xy-y^2+3y+x+2017\)

\(P=\left(x^3+x^2y-2x^2\right)+\left(-xy-y^2+2y\right)+\left(x+y-2\right)+2019\)

\(P=x^2\left(x+y-2\right)-y\left(x+y-2\right)+\left(x+y-2\right)+2019\)

\(P=\left(x^2-y+1\right)\left(x+y-2\right)+2019\)

\(P=0+2019=2019\)